[ ruby-Patches-7760 ] Fix for File and File::Stat to deal with bogus stat.st_size member

Patches item #7760, was opened at 2007-01-11 14:26
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http://rubyforge.org/tracker/?func=detail&atid=1700&aid=7760&group_id=426

Category: Ruby1.8
Group: None
Status: Open
Resolution: None
Priority: 3
Submitted By: Daniel Berger (djberg96)
Assigned to: Nobody (None)
Summary: Fix for File and File::Stat to deal with bogus stat.st_size member

Initial Comment:
Hi all,

It seems that the stat() function has a bug on Solaris 10 (06/06) where it doesn't set the st_size value to NULL for character or block devices. Instead, it seems to default to INT_MAX, which results in bogus information returned by File::Stat.

For example:

irb(main):001:0> File.stat("/dev/fd0").size
=> 9223372036854775807

That should return 0. This has been reported on sunsolve.sun.com (bug 4013608), but I'm not positive if it's been patched yet, or if it affects other Solaris versions, because I don't have a sunsolve account (i.e. I can see the ticket summary but not the details).

This affects the following methods:

File::Stat#size
File::Stat#size?
File::Stat#zero?
File.size
File.size?
File.zero?

I'm not sure if you take patches for bugs in the underlying OS or not. If you do accept them, here's the patch.  I've also included a small test suite that now passes on my Solaris box.  Note that I've only added explicit comments on the approach I use here in one function (rb_stat_size). Copy and paste if you would like it added to each of the functions.

--- file.orig   Tue Jan  9 10:57:09 2007
+++ file.c      Thu Jan 11 14:08:34 2007
@@ -467,7 +467,15 @@
 rb_stat_size(self)
     VALUE self;
 {
-    return OFFT2NUM(get_stat(self)->st_size);
+    struct stat *st = get_stat(self);
+
+    /* Block and character devices are handled explicitly because some
+     * platforms set the st_size member to an incorrect value.
+     */
+    if (S_ISCHR(st->st_mode) || S_ISBLK(st->st_mode))
+        return INT2FIX(0);
+
+    return OFFT2NUM(st->st_size);
 }
 
 /*
@@ -1257,7 +1265,9 @@
     struct stat st;
 
     if (rb_stat(fname, &st) < 0) return Qfalse;
-    if (st.st_size == 0) return Qtrue;
+    if (st.st_size == 0 || S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))
+        return Qtrue;
+
     return Qfalse;
 }
 
@@ -1276,7 +1286,9 @@
     struct stat st;
 
     if (rb_stat(fname, &st) < 0) return Qnil;
-    if (st.st_size == 0) return Qnil;
+    if (st.st_size == 0 || S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))
+        return Qnil;
+
     return OFFT2NUM(st.st_size);
 }
 
@@ -1481,7 +1493,11 @@
     struct stat st;
 
     if (rb_stat(fname, &st) < 0)
-       rb_sys_fail(StringValueCStr(fname));
+        rb_sys_fail(StringValueCStr(fname));
+
+    if( S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode) )
+        return INT2FIX(0);
+
     return OFFT2NUM(st.st_size);
 }
 
@@ -3981,7 +3997,10 @@
 rb_stat_z(obj)
     VALUE obj;
 {
-    if (get_stat(obj)->st_size == 0) return Qtrue;
+    struct stat *st = get_stat(obj);
+    if (st->st_size == 0 || S_ISCHR(st->st_mode) || S_ISBLK(st->st_mode))
+        return Qtrue;
+
     return Qfalse;
 }
 
@@ -4000,10 +4019,11 @@
 rb_stat_s(obj)
     VALUE obj;
 {
-    off_t size = get_stat(obj)->st_size;
+    struct stat *st = get_stat(obj);
+    if (st->st_size == 0 || S_ISCHR(st->st_mode) || S_ISBLK(st->st_mode))
+        return Qnil;
 
-    if (size == 0) return Qnil;
-    return OFFT2NUM(size);
+    return OFFT2NUM(st->st_size);
 }
 
 /*


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http://rubyforge.org/tracker/?func=detail&atid=1700&aid=7760&group_id=426